With thousands of fans packed into stands and royalty in attendance, sporting events are seen as an ideal target for cynical terrorists.

And a wave of British “lone wolf” ­jihadists fresh from the battlegrounds of Syria could be plotting murderous attacks on horse races watched by the Queen as well as Premier League and FA Cup games and tennis matches.

Security surrounding the monarch was tonight stepped up after al-Qaeda chiefs urged terrorists to blow up sports events she is most likely to go and see.

An article on English-language online magazine Inspire, produced by the terror group, also gives tips on car bombing and disguises along with a list of potential high-profile targets around the globe.

The piece, written by an author calling himself the AQ Chef, says: “In the ­beginning of summer we have Cheltenham and [at] the end of summer we have Epsom, whereby horse races are attended by thousands from around the kingdom including the Queen.”

Inspire Magazine: 'Make a bomb in the kitchen of your mom'

Turning his attention to football matches, which in the Premier League pull in weekly crowds of up to 75,000 fans, AQ Chef writes: “The best time is after the final whistle, when huge crowds leave the stadium and celebrate around the entrances.”

Fears of a terrorist attack are on the increase after an estimated 250 British jihadists returned here from training and fighting in Syria’s civil war.

It is believed M15 and MI6’s top five operations all involve tracking war-hardened Brits.

Scotland Yard said it was aware of the inflammatory al-Qaeda article. A spokesman added: “Appropriate steps have been put in place, including providing relevant security advice.”

While the Cheltenham festival earlier this month passed off peacefully, there are still fears for the Queen’s trip to Epsom for the Derby in the summer.

She attends the race, which is on June 7, religiously, every year along with other members of the Royal Family.

Target: Queen at Royal Ascot (Image: Reuters)

The Queen also attends every day of Royal Ascot each year where she takes part in a carriage procession before the races start. That would make her an easy target for terrorists.

As well as the call to attack sporting events, the Inspire article also lists several major targets in Britain, America and France, including London’s Savoy Hotel, the Dordogne Valley, Bastille Military Day Parade, the Louvre art gallery and Sears Tower in Chicago.

The magazine is produced by the al-Qaeda in the Arab Peninsula, believed to be the group’s most ruthless branch.

Comment: Lone wolves should not be underestimated

Colonel Richard Kemp, former Head of International Terrorist Intelligence for COBRA

Major sporting events have long been on al-Qaeda’s list of targets.

Huge crowds in packed stadiums can make security checks very difficult and lead to mass casualties.

When televised live they give the terrorists what they want – footage that will be beamed around the world.

Although Inspire’s authors know the chances of getting near the Queen are remote, they realise attacking a venue where she is present will be huge news.

Calling for “lone wolf” attacks is a sign of al-Qaeda’s desperation. Their central organisation in Pakistan has been decimated by US drone strikes.

Many jihadists have been killed by our troops in Afghanistan.

Networks in the UK have been penetrated by the hugely effective undercover intelligence work of MI5 and the police. Despite dozens of attempts, al-Qaeda has failed to mount a successful attack here since 2005.

But lone wolves should not be underestimated. Just look at the vicious murder of Drummer Lee Rigby.

Acting alone or in small teams, lone wolves don’t need to communicate and plan in a way that exposes them to discovery by the security services.

And there will be no shortage of volunteers among British jihadists who return from fighting in Syria.